fix: keep tool child stdin closed and run tool commands non-interactively

[utk-code]

Issue for this PR
Closes #42773

Type of change

• Bug fix
• New feature
• Refactor / code improvement

What does this PR do?
On Windows, tool commands that prompt for input on stdin (e.g. npm exec asking "Ok to proceed? (y)") hang — the prompt shows up but nothing typed reaches the process, because the child's stdin is an open pipe nothing closes, and the TUI owns the console input.

Changes:

• Spawner default for child stdin changed from open pipe to closed ("ignore"). Callers passing explicit stdin are unaffected.
• Shell/bash tool commands now get CI=1, npm_config_yes=true, GIT_TERMINAL_PROMPT=0, NONINTERACTIVE=1, so tools like npm skip interactive prompts.

How did you verify your code works?
Reproduced on Windows: npm exec with an open stdin pipe hangs; with CI=1 or npm_config_yes=true it completes. Checked no tests rely on the old default.

Screenshots / recordings
N/A (not a UI change)

Checklist

• I have tested my changes locally
• I have not included unrelated changes in this PR

[github-actions]

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[github-actions]

The following comment was made by an LLM, it may be inaccurate:

Based on my search, I found one potentially related PR:

PR #41968: fix(cli): survive broken stdio pipes
#41968

This PR may be related as it also deals with stdio/pipe handling in child processes, though it focuses on surviving broken pipes rather than closing stdin and preventing interactive prompts.

However, the current PR #42778 appears to be a unique fix addressing the specific issue (#42773) where tool commands hang on Windows due to open stdin pipes and interactive prompts. No exact duplicates were found.

[github-actions]

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